Core B will provide a constant resource of mice harboring melanomas that express BRAF*, including pairs of tumor biopsies that are sensitive or resistant to BRAFi. The integrative power of this core lies in interacting and intersecting with parallel samples from human melanomas in Core A, providing cross-species triangulation of genetic elements that confer tumor microenvironment-specific phenotypic effects. This core will provide not only a bank of Braf* mouse (iBIP and M3) melanoma tissues and derivative cell lines collected at baseline, post-treatment and upon relapse, but also capability to engineer new alleles ex vivo and perform preclinical therapeutic studies. The immunocompetent background and natural tumor microenvironment setting of IBIP melanomas bring a key feature to this TMEN center.